4 New Reasons You Should Know Your Blood Type

By Lauren Gelman

What’s in a blood type? Potentially a lot, according to several recent studies that correlate different blood groups with everything from risk of heart disease to infertility. While none of these studies are conclusive about cause and effect (they can’t say X blood type causes Y disease) and any increased risks are still pretty small, the research does highlight the importance of knowing your type—A, B, AB, or O—and how it could affect your wellbeing.

1. Blood clots: Type AB, A, and B increases risk
Danish researchers recently studied how blood type interacts with a genetic predisposition for deep-vein thrombosis (DVT), or blood clots in the lower legs that can travel to the lungs and become life threatening. After analyzing data on about 66,000 people over more than 30 years, they found that those with type AB, A, or B, had a 40 percent higher risk of DVT than people with type O, the most common type.

When the scientists did further analysis to see which factors have the biggest impact on DVT risk on a population level, they found that an AB blood type contributed to about 20 percent of blood clots; genetic mutations accounted for 11 percent, being overweight accounted for 16 percent, and smoking accounted for 6 percent, reported Time.com.

2. Heart disease: Type AB, B and A all increase risk
When Harvard scientists analyzed more than two decades of data on more than 77,000 people, they found that those with AB blood had a 23 percent increased risk for heart disease compared to people with type O blood. Those with type B blood had an 11 percent higher risk and those with type A blood had 5 percent greater risk. Researchers aren’t sure why, according to HealthDay, but posit that type A blood is associated with LDL cholesterol and that type O blood, which is associated with reduced risk, may contain a chemical that boosts blood flow and prevents clots.

However, researchers are quick to point out that lifestyle factors like weight, smoking, and diet, which, unlike blood type, are modifiable, have a much greater impact on heart disease.

3. Stomach cancer: Type A increases risk

People with blood group A had a 20 percent greater chance of developing gastric cancer compared to people with blood groups O and B, according to a 2010 Swedish study from the Karolinska Institute. These people may be more vulnerable to other stomach cancer risk factors such as cigarette and alcohol use, according to DailyMail.co.uk.

Meanwhile, the same Swedish paper found that those with type O blood had an increased risk for stomach ulcers; they may be more susceptible to the Helicobacter pylori bacteria that cause the stomach sores.

4. Fertility: Type O reduces it

Women with this blood type were twice as likely to have blood levels of the hormone FSH high enough to indicate low ovarian reserve, a measure of fertility, according to an Albert Einstein College of Medicine study. Researchers couldn’t say for sure why, though. Given that type O blood is the most prevalent across all U.S. ethnicities, it doesn’t pay to worry too much about it. Age is a far more important risk factor for fertility problems, the study author told New Scientist.